The Vatican is enlisting more big-name consulting firms to advise it on structural and financial reforms, tapping McKinsey & Co to help modernise its communications operations and KPMG to bring its accounting up to international standards.

The decision was announced on Thursday by the commission of inquiry into the Vatican's financial and organisational health created in July by Pope Francis as part of his plans to overhaul the antiquated and often-times dysfunctional Vatican bureaucracy.

Already, regulatory compliance firm Promontory Financial Group has installed two dozen people at the troubled Vatican bank to review its accounts and make sure they conform to international norms to fight money-laundering and terror financing.

Promontory is also advising the Vatican's other main financial institution, APSA, which administers the Vatican's real estate.

Meanwhile, the Vatican City State, which controls the money-making Vatican Museums and duty-free department store, appointed consulting firm EY (Ernst & Young) to check its books.

Francis was elected pope on a mandate from cardinals to reform the Vatican bureaucracy and make it more responsive to the needs of the 21st Century Catholic Church.

He has tapped eight key cardinals from around the globe to advise him, and appointed a handful of study commissions to offer expertise.

The first main proposals are expected to be floated when the cardinals meet for a third time with Francis in January.

The Vatican said McKinsey would be reviewing the Vatican's many communications operations and would make recommendations on how to make them "more functional, efficient and modern."

The Vatican spokesman, the reverend Federico Lombardi, said the work should take about two or three months.

The Holy See, which has long suffered from communications problems, has a host of official news outlets and media offices that helps get out its message out, but they all are run independently and report to different offices: There's Lombardi's spokesman's office, the official Vatican Radio, Vatican Television, Vatican publishing house and the Vatican newspaper L'Osservatore Romano.

In recent years, the Vatican has also developed a whole operation for new media, which includes its news.va web portal, which is run by its social communications department.

The announcement of the new consultants was made ahead of Francis' Christmas address on Saturday to the Vatican Curia, or administration, which will be watched for hints of the direction Francis might take the reform.

The Vatican's financial and organisational problems, known to church insiders, were revealed publicly last year with the leaks of papal correspondence by then-Pope Benedict XVI's butler.

The documents exposed turf battles, allegations of corruption in the awarding of Vatican contracts and enormous fiscal waste, including the €550,000 ($919,820) the Holy See spent in 2009 for its Christmas Nativity scene in St. Peter's Square. (For the last two years, the creches have been donated).

More recently, the Vatican was rocked by the arrest of its APSA accountant on charges he tried to smuggle €20 million into Italy from Switzerland.

The accountant, who had several Vatican bank accounts, is also accused of money laundering in a separate case. He has said he was only trying to help friends.